The retinitis pigmentosa 2 (X-linked recessive) (RP2) gene exists on the short arm of the human chromosome X, and it is known as a causal gene of retinitis pigmentosa (Nat Genet. 1998; 19(4): 327-332). RP2 is known to have a function to bind to ARL3 (ADP ribosylation factor like GTPase 3), which is one of the small GTPase protein family members, to enhance GTP hydrolase activity of ARL3, i.e. it is a GTPase activating protein (Nat Struct Mol Biol. 2008; 15(4): 373-380). Its association with cancer is currently unknown.
Rho GTPase activating protein 6 (ARHGAP6) gene, which has GTPase activating function, exists on the short arm of human chromosome X, same as RP2, and the protein encoded by this gene is a GTPase activating protein possessing a Rho-GAP domain at the center. The ARHGAP6 gene is known to have a function of enhancing the GTP hydrolase activity of the small GTPase protein family, particularly RhoA (Hum Mol Genet. 2000; 9(4): 477-488). With regards to cancer, it is reported that the gene has decreased its expression in the African American population, which has a high incidence rate and mortaility rate of colon cancer (PLoS One. 2012; 7(1): e30168), and also that a fusion gene thereof with a claudin 18 (CLDN18) gene was found in patients suffered from diffuse type gastric cancer (Nature 2014; 513(7517): 202-209).
There are no reports so far of a fusion gene composed of RP2 and ARHGAP6.